Multiwall bag



A ril 26, 1966 A. J. BURKE MULTIWALL BAG Filed 001;. 21. 1964 FIG. 2

FIG. 3

FIG. I

INVENT OR AR THUR .1. BURKE ATTORNEYS United States Patent 3,248,041 MULTIWALL BAG Arthur J. Burke, Oakland, N.J.,'assignor to Howe Richardson Scale Company, Clifton, NJ., a corporation of Delaware Filed Oct. 21, 1964, Ser. No. 405,392 10 Claims. (Cl. 229-55) This invention relates to multiwall bags and particularly to such bags having an inner ply of air tight plastic or the like and provided with a special air vent arrangement to prevent bursting of the bag during forcible packing with flour and like solid substances.

Flour and other substances are usually'packed with considerable pressure into bags, the substance being forced into the bag as by an auger type feed. In the past conventional multiwall paper bags were employed, and the paper was of suflicient porosity that air displaced from the substance vented directly through the paper.

More recently it has become customary to provide multiwall paper and other bags with an inner ply of thin highly flexible sheet plastic, such as polyvinyl chloride were food is packaged, such bags comprising for example inner and outer paper layers with an intermediate ply of air tight plastic which may be sealed at least along the top and bottom edges, so that a completely water and air tight package is provided. Bags of this construction however cannot be filled by packing because the air impervious ply prevents displaced air from escaping the bag and often the bags will balloon and even burst during the packing process.

The present invention solves the problem of utilizing these desirable plastic internal sheet liners or plys in multi- 'wall bags for packing, by providing an air venting ply or liner between the inner wall of the .bag and the air tight ply.

It is therefore the major object of this invention to provide a novel multiwall bag construction wherein an air vent layer, liner, ply or the like is provided between the inner substance contact wall and the air tight ply, which is preferably thin highly flexible polyvinyl chloride sheeting or equivalent. Pursuant to this object the air vent layer may be corrugated paper, crepe paper, open work fabric or any like material capable of maintaining an air escape path to the bag edges While the interior is being subjected to expanding type packing operations.

Further objects .of the invention will appear as the description proceeds in connection with the appended claims and the annexed drawings wherein:

FIGURE 1 is a section diagrammatically showing a multiwall bag of the type in which the invention may be incorporated;

FIGURE 2 is a fragmentary enlarged section on line 22 of FIGURE 1;

FIGURE 3 is a fragmentary section on line 3-3 of FIGURE 2;

FIGURE 4 is a fragmentary section similar to FIGURE 2 but incorporating a ditferent air vent ply; and

FIGURE 5 is a fragmentary view showing an open work fabric used as the air vent ply in FIGURE 4.

FIGURE 1 shows one type of bag in which the invention may be incorporated. When the top flaps are sealed after packing, the entire package is water and air tight.

FIGURES 2 and 3 show one preferred wall structure comprising an inner paper ply wall 11, an air vent ply 12, a highly flexible ply of air impervious plastic sheet material 13, here polyvinyl chloride, and an outer paper ply wall 14.

In this embodiment the air vent ply is a sheet of crepe paper sufficiently resistant to crushing to withstand packing pressures for maintaining continuously open air vent channels or reliefs to the edges of the open mouth of the bag during filling. This is diagrammatically shown in FIGURES 2 and 3.

Thus, as the flour or like substance packs within inner paper layer 11, displaced air will pass through the relatively porous paper and will vent through the crepe paper passages, so that the bag is protected against entrapped air pockets and possible bursting.

Similarly FIGURES 4 and 5 show another type of air venting ply wherein a sheet of open net fabric 15 is interposed between the inner paper ply and the plastic ply, thereby providing for escape of air from the interior of the plastic liner when the bag is packed with flour or other like contents.

The invention may be applied to substantially any multiwall bag combination, and it is necessary only that the air vent ply lines the air impervious ply to protect it against bursting.

The bags of the invention usually originate from tubular multiwall lengths which are cut to length and the bottom flaps folded over and sealed air tight as shown in FIG- URE 1. After filling the upper flaps or sides are interfolded into airtight sealing relation.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by Letters Patent is:

1. A multiwall bag construction consisting essentially of an inner air pervious substance containing layer, an air impervious layer disposed outwardly of said inner layer, an air vent layer disposed intermediate said other two layers, and an outer layer of air pervious material around said air impervious layer. I

2. The multiwall bag structure defined in claim 1 wherein said inner layer is paper. I

3. The multiwall bag structure defined in claim 1,

wherein said air impervious layer is a thin sheet of flexible plastic.

4. The multiwall bag structure defined in claim 3 wherein said air impervious plastic layer is polyvinyl chloride.

5. The multiwall bag structure defined in claim 1,

wherein said air vent layer comprises a sheet of crepe paper.

6. The multiwall bag structure defined in claim 1 wherein said air vent layer is an open work fabric.

7. The multiwall bag structure defined in claim 1 wherein said air vent layer is a corrugated sheet material.

8. A multiwall bag structure for the forcible packing of solids comprising inner and outer plies of paper ,with an internal liner of flexible air impervious plastic secured within the outer paper ply and an intermediate air vent ply located within the air impervious ply whereby when said material is packedwithin the bag displaced air escapes through passages in said air vent ply to the open end of the bag being filled.

9. A multiwall bag construction consisting essentially of an inner air perv-ions substance containing layer, an air layers, and an outer layer of paper extending around said air impervious layer. p v v I H 10. A multiwall bag structure for the forcible packing of a solid substance comprising an inner ply of air pervious sheet material such as paper adapted to directly contain said substance, an outer ply coextensively surrounding said inner ply and having at least on its inner side a layer of flexible air impervious plastic, and an intermediate air vent ply located between said air impervious layer and said inner ply whereby when said substance is being packed within the bag displaced 'air escape-s through passages in said air vent ply to the open end of the bag being filled. I

References Cited by the Examiner 7 r UNITED STATES PATENTS FOREIGN PATENTS 5/1960 Canada. 3/1955 Italy.

10 JOSEPH R. LECLAIR, Primary Examiner.

D. M. BOCKENEK, Assistant Examiner. 

1. A MULTIWALL BAG CONSTRUCTION CONSISTING ESSENTIALLY OF AN INNER AIR PERVIOUS SUBSTANCE CONTAINING LAYER, AN AIR IMPERVIOUS LAYER DISPOSED OUTWARDLY OF SAID INNER LAYER, AN AIR VENT LAYER DISPOSED INTERMEDIATE SAID OTHER TWO LAYERS, AND AN OUTER LAYER OF AIR PERVIOUS MATERIAL AROUND SAID AIR IMPERVIOUS LAYER. 